This invention relates to an improved revolving table for book-binding stackers and the like.
As is known, stackers are machines positioned downstream of book-binding equipment, such as collators, where they function to form stacks of sheets, signatures, pamphlets, brochures, or the like, upon arrival from said book-binding equipment.
Since, in the instance of brochures or signatures, the same would have a back or spine side which assumes a larger thickness dimension along the fold side than the remaining portions of the brochures or signatures, in order to avoid the formation of fanned-out, and consequently unstable, stacks, it is common practice to lay the stacks onto a revolving table which can be rotatively reciprocated through 180 degrees and, upon the formation of each single layer in the stacks, is rotated by 180.degree. to form the next layer. Arranged orthogonally to the direction of arrival of the signatures or the like, a conveyor belt is associated with the system for the removal of the completed stacks. To transfer the stacks from the revolving table onto the stack removing conveyor belt, in a conventional construction, a cylinder-piston unit is associated with the stationary stacker frame, the free end of the piston rod whereof has a pusher secured thereto, which pusher is, in its inoperative or home position, located in front of the revolving table, substantially on the same plane as the table.
Said cylinder-piston unit extends in the direction of movement of the stack conveyor belt and sticks out of the stacker frame in cantilever relationship therewith.
The pusher performs its movements on the revolving table.
Such prior stackers have several deficiencies and disadvantages, among which the following stand out.
(a) The stacker bulk dimensions are increased considerably by the provision of the cantilevered cylinder-piston unit for actuating the pusher. This entails increased space requirements in a book-binding environment where, as is well known, space is at a premium and not always available.
(b) Since the pusher is external to the revolving table and separate from it, the result is that the revolving table must be allowed fairly large overall dimensions to prevent the pusher, while stationary, from interfering with the stack corners during the table rotation. This reflects, on one hand, in a further increase of the stacker size, and on the other hand, in the need for a longer stack-ejecting stroke of the pusher.
(c) Upon completion of the stack-ejecting stroke, the pusher must be returned to its initial position, before another stack-ejecting stroke can take place. Therefore, each stack-ejecting stroke is followed by an idle, that is inactive, stroke. This, of course, considerably reduces the number of stack-ejecting cycles per unit time.
(d) It is only possible to eject the stacks in one direction, that is in the pusher direction of movement. This involves the use of a single conveyor for stack removal, whereas in many cases it would be desirable to use two or more stack conveyor belts set at an angle to each other, e.g. at 90.degree. or 180.degree..
(e) The procedure for adapting a stacker to its associated book-binding machine, e.g. a collator, or to get the oncoming stacks aligned, requires several manual operations and a number of movable parts.